Answer to Question #268340 in Organic Chemistry for aish

Question

hi, help answer this question please.

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1) s- limonene has a specific optical rotation of 94 degree.the

commercially supplied mixture of the latter has a 95% enentiometric excess (ee)

1d) what is the observed specific rotation of the above commercial mixture? (12marks)

1e)what percentage of each enantiomer is present in the above commercial mixture (95% ee in favour of S) (6marks)

Answer 1

It is expressed as a percentage. If the sample only rotates plane-polarized light half as much as expected, the optical purity is 50%. For example, a mixture containing 60% R enantiomer (and 40% S enantiomer) has a 20% enantiomeric excess of R: ((60-50) x 100) / 50 = 20 %.

Specific rotation ([α]) is a property of a chiral chemical compound. It is defined as the change in orientation of monochromatic plane-polarized light, per unit distance–concentration product, as the light passes through a sample of a compound in solution.